rpc: deduplicate WriteHDKeypath() used in decodepsbt

The functionality is already provided in the BIP32 utility library util/bip32.h
with the exact same name and function signature.

Author: theStack

src/rpc/rawtransaction.cpp

@@ -28,6 +28,7 @@
 #include <script/signingprovider.h>
 #include <script/standard.h>
 #include <uint256.h>
+#include <util/bip32.h>
 #include <util/moneystr.h>
 #include <util/strencodings.h>
 #include <util/string.h>
@@ -938,25 +939,6 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
     return result;
 }
 
-static std::string WriteHDKeypath(std::vector<uint32_t>& keypath)
-{
-    std::string keypath_str = "m";
-    for (uint32_t num : keypath) {
-        keypath_str += "/";
-        bool hardened = false;
-        if (num & 0x80000000) {
-            hardened = true;
-            num &= ~0x80000000;
-        }
-
-        keypath_str += ToString(num);
-        if (hardened) {
-            keypath_str += "'";
-        }
-    }
-    return keypath_str;
-}
-
 UniValue decodepsbt(const JSONRPCRequest& request)
 {
             RPCHelpMan{"decodepsbt",